/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2000-2002,2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xerces.internal.impl.io;

import java.io.InputStream;
import java.io.IOException;
import java.io.Reader;

import com.sun.xml.internal.stream.util.BufferAllocator;
import com.sun.xml.internal.stream.util.ThreadLocalBufferAllocator;

/**
 * Reader for UCS-2 and UCS-4 encodings.
 * (i.e., encodings from ISO-10646-UCS-(2|4)).
 *
 * @author Neil Graham, IBM
 * @xerces.internal
 */
public class UCSReader extends Reader {

  //
  // Constants
  //

  /**
   * Default byte buffer size (8192, larger than that of ASCIIReader
   * since it's reasonable to surmise that the average UCS-4-encoded
   * file should be 4 times as large as the average ASCII-encoded file).
   */
  public static final int DEFAULT_BUFFER_SIZE = 8192;

  public static final short UCS2LE = 1;
  public static final short UCS2BE = 2;
  public static final short UCS4LE = 4;
  public static final short UCS4BE = 8;

  //
  // Data
  //

  /**
   * Input stream.
   */
  protected InputStream fInputStream;

  /**
   * Byte buffer.
   */
  protected byte[] fBuffer;

  // what kind of data we're dealing with
  protected short fEncoding;

  //
  // Constructors
  //

  /**
   * Constructs an ASCII reader from the specified input stream
   * using the default buffer size.  The Endian-ness and whether this is
   * UCS-2 or UCS-4 needs also to be known in advance.
   *
   * @param inputStream The input stream.
   * @param encoding One of UCS2LE, UCS2BE, UCS4LE or UCS4BE.
   */
  public UCSReader(InputStream inputStream, short encoding) {
    this(inputStream, DEFAULT_BUFFER_SIZE, encoding);
  } // <init>(InputStream, short)

  /**
   * Constructs an ASCII reader from the specified input stream
   * and buffer size.  The Endian-ness and whether this is
   * UCS-2 or UCS-4 needs also to be known in advance.
   *
   * @param inputStream The input stream.
   * @param size The initial buffer size.
   * @param encoding One of UCS2LE, UCS2BE, UCS4LE or UCS4BE.
   */
  public UCSReader(InputStream inputStream, int size, short encoding) {
    fInputStream = inputStream;
    BufferAllocator ba = ThreadLocalBufferAllocator.getBufferAllocator();
    fBuffer = ba.getByteBuffer(size);
    if (fBuffer == null) {
      fBuffer = new byte[size];
    }
    fEncoding = encoding;
  } // <init>(InputStream,int,short)

  //
  // Reader methods
  //

  /**
   * Read a single character.  This method will block until a character is
   * available, an I/O error occurs, or the end of the stream is reached.
   *
   * <p> Subclasses that intend to support efficient single-character input
   * should override this method.
   *
   * @return The character read, as an integer in the range 0 to 127 (<tt>0x00-0x7f</tt>), or -1 if
   * the end of the stream has been reached
   * @throws IOException If an I/O error occurs
   */
  public int read() throws IOException {
    int b0 = fInputStream.read() & 0xff;
    if (b0 == 0xff) {
      return -1;
    }
    int b1 = fInputStream.read() & 0xff;
    if (b1 == 0xff) {
      return -1;
    }
    if (fEncoding >= 4) {
      int b2 = fInputStream.read() & 0xff;
      if (b2 == 0xff) {
        return -1;
      }
      int b3 = fInputStream.read() & 0xff;
      if (b3 == 0xff) {
        return -1;
      }
      System.err.println(
          "b0 is " + (b0 & 0xff) + " b1 " + (b1 & 0xff) + " b2 " + (b2 & 0xff) + " b3 " + (b3
              & 0xff));
      if (fEncoding == UCS4BE) {
        return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
      } else {
        return (b3 << 24) + (b2 << 16) + (b1 << 8) + b0;
      }
    } else { // UCS-2
      if (fEncoding == UCS2BE) {
        return (b0 << 8) + b1;
      } else {
        return (b1 << 8) + b0;
      }
    }
  } // read():int

  /**
   * Read characters into a portion of an array.  This method will block
   * until some input is available, an I/O error occurs, or the end of the
   * stream is reached.
   *
   * @param ch Destination buffer
   * @param offset Offset at which to start storing characters
   * @param length Maximum number of characters to read
   * @return The number of characters read, or -1 if the end of the stream has been reached
   * @throws IOException If an I/O error occurs
   */
  public int read(char ch[], int offset, int length) throws IOException {
    int byteLength = length << ((fEncoding >= 4) ? 2 : 1);
    if (byteLength > fBuffer.length) {
      byteLength = fBuffer.length;
    }
    int count = fInputStream.read(fBuffer, 0, byteLength);
    if (count == -1) {
      return -1;
    }
    // try and make count be a multiple of the number of bytes we're looking for
    if (fEncoding >= 4) { // BigEndian
      // this looks ugly, but it avoids an if at any rate...
      int numToRead = (4 - (count & 3) & 3);
      for (int i = 0; i < numToRead; i++) {
        int charRead = fInputStream.read();
        if (charRead == -1) { // end of input; something likely went wrong!A  Pad buffer with nulls.
          for (int j = i; j < numToRead; j++) {
            fBuffer[count + j] = 0;
          }
          break;
        } else {
          fBuffer[count + i] = (byte) charRead;
        }
      }
      count += numToRead;
    } else {
      int numToRead = count & 1;
      if (numToRead != 0) {
        count++;
        int charRead = fInputStream.read();
        if (charRead == -1) { // end of input; something likely went wrong!A  Pad buffer with nulls.
          fBuffer[count] = 0;
        } else {
          fBuffer[count] = (byte) charRead;
        }
      }
    }

    // now count is a multiple of the right number of bytes
    int numChars = count >> ((fEncoding >= 4) ? 2 : 1);
    int curPos = 0;
    for (int i = 0; i < numChars; i++) {
      int b0 = fBuffer[curPos++] & 0xff;
      int b1 = fBuffer[curPos++] & 0xff;
      if (fEncoding >= 4) {
        int b2 = fBuffer[curPos++] & 0xff;
        int b3 = fBuffer[curPos++] & 0xff;
        if (fEncoding == UCS4BE) {
          ch[offset + i] = (char) ((b0 << 24) + (b1 << 16) + (b2 << 8) + b3);
        } else {
          ch[offset + i] = (char) ((b3 << 24) + (b2 << 16) + (b1 << 8) + b0);
        }
      } else { // UCS-2
        if (fEncoding == UCS2BE) {
          ch[offset + i] = (char) ((b0 << 8) + b1);
        } else {
          ch[offset + i] = (char) ((b1 << 8) + b0);
        }
      }
    }
    return numChars;
  } // read(char[],int,int)

  /**
   * Skip characters.  This method will block until some characters are
   * available, an I/O error occurs, or the end of the stream is reached.
   *
   * @param n The number of characters to skip
   * @return The number of characters actually skipped
   * @throws IOException If an I/O error occurs
   */
  public long skip(long n) throws IOException {
    // charWidth will represent the number of bits to move
    // n leftward to get num of bytes to skip, and then move the result rightward
    // to get num of chars effectively skipped.
    // The trick with &'ing, as with elsewhere in this dcode, is
    // intended to avoid an expensive use of / that might not be optimized
    // away.
    int charWidth = (fEncoding >= 4) ? 2 : 1;
    long bytesSkipped = fInputStream.skip(n << charWidth);
    if ((bytesSkipped & (charWidth | 1)) == 0) {
      return bytesSkipped >> charWidth;
    }
    return (bytesSkipped >> charWidth) + 1;
  } // skip(long):long

  /**
   * Tell whether this stream is ready to be read.
   *
   * @return True if the next read() is guaranteed not to block for input, false otherwise.  Note
   * that returning false does not guarantee that the next read will block.
   * @throws IOException If an I/O error occurs
   */
  public boolean ready() throws IOException {
    return false;
  } // ready()

  /**
   * Tell whether this stream supports the mark() operation.
   */
  public boolean markSupported() {
    return fInputStream.markSupported();
  } // markSupported()

  /**
   * Mark the present position in the stream.  Subsequent calls to reset()
   * will attempt to reposition the stream to this point.  Not all
   * character-input streams support the mark() operation.
   *
   * @param readAheadLimit Limit on the number of characters that may be read while still preserving
   * the mark.  After reading this many characters, attempting to reset the stream may fail.
   * @throws IOException If the stream does not support mark(), or if some other I/O error occurs
   */
  public void mark(int readAheadLimit) throws IOException {
    fInputStream.mark(readAheadLimit);
  } // mark(int)

  /**
   * Reset the stream.  If the stream has been marked, then attempt to
   * reposition it at the mark.  If the stream has not been marked, then
   * attempt to reset it in some way appropriate to the particular stream,
   * for example by repositioning it to its starting point.  Not all
   * character-input streams support the reset() operation, and some support
   * reset() without supporting mark().
   *
   * @throws IOException If the stream has not been marked, or if the mark has been invalidated, or
   * if the stream does not support reset(), or if some other I/O error occurs
   */
  public void reset() throws IOException {
    fInputStream.reset();
  } // reset()

  /**
   * Close the stream.  Once a stream has been closed, further read(),
   * ready(), mark(), or reset() invocations will throw an IOException.
   * Closing a previously-closed stream, however, has no effect.
   *
   * @throws IOException If an I/O error occurs
   */
  public void close() throws IOException {
    BufferAllocator ba = ThreadLocalBufferAllocator.getBufferAllocator();
    ba.returnByteBuffer(fBuffer);
    fBuffer = null;
    fInputStream.close();
  } // close()

} // class UCSReader
